This invention relates to an apparatus and method for forming a concrete block in which one or more surfaces of the block are irregular in appearance, providing a rough texture resembling that of a split block.
In the manufacture of concrete blocks, it is known to split a cured composite block module along one or more splitting planes to provide an irregular surface to the block. This procedure typically produces waste material from the splitting operation. The split appearance of the block surface is esthetically desirable in many applications. Splitting of blocks in this manner can take place only along a splitting plane, resulting in a substantially planar block face having an irregular surface at the split. This type of block forming is known in the art, and is generally acceptable for applications in which a planar split surface is desired.
In some applications, it is desirable to provide a block surface which is non-planar. In the past, it has not been possible to provide a non-planar split block surface, due to the limitations of block splitting technology.
Haines U.S. Pat. No. 3,981,953 shows a method of forming a fractured block face in which block material is placed into a mold cavity, with a grid-like series of elements being disposed within the cavity and suspended from a top plate. After the block material is compacted into the cavity, the sidewalls and top plate are drawn off the block formed by the material. Upward movement of the top plate lifts the grid-like series of elements, and the block material between the elements and the lower plate is broken off of the lower block material, leaving a fractured face thereon. A drawback to this arrangement is that the pattern of the elements is essentially cast into place in the block face.
The present invention is designed to address the above-noted problems, and to provide an apparatus and method for forming a block having an irregular split-type surface, in which the irregular or split-type surface need not be a planar surface. In addition, it is an object of the invention to provide a block forming apparatus and method which is capable of quickly and efficiently forming an irregular split-type block surface, either on an inside or an outside surface of the block.
In accordance with the invention, an apparatus for forming an irregular surface block comprises a cavity, a first portion of which is designed to retain therewithin block forming material providing an irregular surface, and a second portion of which is adapted to receive block forming material therewithin to form the block. The apparatus further comprises means for removing the block formed by the block forming material from the second portion of the cavity after the material has been in the cavity a short period of time, and before it begins to cure. In a preferred embodiment, a lower support plate is positioned below the portion of the cavity in which the block is formed, with the block forming material being placed above the support plate. Upon removal of the block from the cavity, the block forming material in the first portion of the cavity remains in place, forming an outer surface on the block having a split-type appearance.
In one embodiment of the apparatus, a split-type irregular surface is provided on an outer surface of the block. In this embodiment, the first and second portions of the cavity are defined by a bottom wall and one or more upstanding side walls. In a preferred form, the one or more upstanding side walls include a face plate assembly having a series or projections extending toward the cavity, with the face plate assembly defining the forward wall and lateral rearward extent of the first portion of the cavity. The projections on the face plate assembly act to retain the material within the first portion of the cavity. The cavity may be formed to any satisfactory shape as desired to define the shape of the irregular outer surface area of the block. A rectangular block can be provided with a single irregular outer face by constructing the face plate assembly so as to retain material within the first portion of the cavity to provide a single irregular surface facing the second portion of the cavity. Upon removal of the block from the second portion of the cavity, the irregular surface provided by the material retained in the first portion of the cavity provides the single irregular face to the block. Alternatively, an irregular surface can be formed to varying configurations as desired by varying the shape of the face plate assembly, and thereby the configuration of material retained within the first portion of the cavity. As yet another alternative, an irregular surface can be formed around the entire outer surface of the block by constructing the cavity so that material is retained within an outer portion of the cavity around the entire periphery of the cavity. The block is then formed in the interior portion of the cavity and, when removed from the cavity, the irregular surface provided by the material retained in the outer portion of the cavity forms an irregular surface on the entire outer surface area of the block. This feature of the invention allows a cylindrical block to be produced which has a split-type appearance on its entire exterior surface, providing a very unusual and desirable block. Other closed geometric-shaped blocks can be obtained in the same manner by constructing the cavity to provide the desired configuration.
In another embodiment of the invention, a split-type irregular surface is provided on an interior surface of the block. This embodiment is useful when forming a composite module from which a pair of split blocks are obtained. The module need only be split along a single splitting plane to provide the pair of blocks, but second surfaces having a split-type appearance along a different plane are obtained by the irregular surfaces which were formed on the interior surfaces of the module. In this embodiment, a core forming assembly is adapted to extend through the cavity, with the core forming assembly being provided with means to retain block forming material therewithin. Withdrawing the core forming assembly from the cavity provides the block forming material within the cavity with an irregular interior surface. The core forming assembly may be provided with spaced core areas across the width of the module, for providing a split-type appearance to an interior surface of the module at more than one location.
The invention further contemplates a method of forming a block, substantially in accordance with the foregoing description.
The block forming apparatus and method summarized above allows blocks having a split-type face to be produced quickly and efficiently, and with a minimum of waste block material.